Optical instrument for determining the distance between two measuring points

ABSTRACT

An improvement in an optical measuring instrument intended for the determination of the distance between two measuring points projected onto a basel plane. The basic device comprises a central optical element with a semi-transparent surface and a totally reflecting surface at a right angle thereto. The device also comprises an outer optical element, such as a mirror or a pentagonal prism, arranged in each beam path between the central optical element and each measuring point, which deflects each respective beam path at a right angle. According to the invention, the central optical element is rotatable about an axis which is parallel to the semi-transparent surface as well as to the totally reflecting surface. By rotating the central optical element one beam will sweep in a plane in space which is defined by the parallel beam paths from the outer optical elements to the measuring points. The device is therefore capable of being employed to determine the location of a random point relative to that plane.

United States/Patent 1 Niss [ 1 Apr. 3, 1973 [54] OPTICAL INSTRUMENT FORDETERMINING THE DISTANCE BETWEEN TWO MEASURING POINTS [75] Inventor:Erik Niss, Liding o, Sweden [73] Assignee: Age Altt iebolag,iidingofsweden [22] Filed: May 21, 1971 21 Appl. No.: 145,799

[52] US. Cl. ..356/3, 356/9, 356/15 [51] Int. Cl. ..G0lc 3/00 [58] Fieldof Search ..356/3, 9,15,17,19, 32

[56] References Cited UNITED STATES PATENTS 2,050,186 10/1936Klemperer...' ..356/32 1,147,990 7/1915 Von l-lofe ..356/l9 1,247,18511/1917 Von Hofe ..356/l9 Primary ExaminerWilliam L. Sikes AssistantExaminer-F. L. Evans AttorneyLarson, Taylor & Hinds [57] ABSTRACT Animprovement in an optical measuring instrument intended for thedetermination of the distance between two measuring points projectedonto a basel plane. The basic device comprises a central optical elementwith a semi-transparent surface and a totally reflecting surface at aright angle thereto. The device also comprises an outer optical element,such as a mirror or a pentagonal prism, arranged in each beam pathbetween the central optical element and each measuring point, whichdeflects each respective beam path at a right angle. According to theinvention, the central optical element is rotatable about an axis whichis parallel to the semi-transparent surface as well as to the totallyreflecting surface. By rotating the central optical element one beamwill sweep in a plane in space which is defined by the parallel beampaths from the outer optical elements to the measuring points. Thedevice is therefore capable of being employed to determine the locationof a random point relative to that plane.

3 Claims, 2 Drawing Figures IO M . 2/ L\ASER o OPTICAL WSTRUMENT FORDETERMINING THE DISTANCE BETWEEN TWO MEASURING POINTS BACKGROUND OF THEINVENTION The present invention relates to an improvement in an opticalmeasuring instrument for determining the distance between two measuringpoints projected onto a basal plane. The measuring instrument is of atype which comprises a central optical element with a semitransparentsurface and a totally reflecting surface at a right angle to it, with anouter optical element, such as a mirror or a prism, being present ineach beam path between this central optical element and each of thepoints, which deflects the respective beam path at a right angle.

An instrument of this type is adjusted through alteration of the.distance between the outer optical elements, and possibly also throughinclination of a line through these outer optical elements, until theparallel beam paths which emanate from the outer optical elements meetthe respective measuring point. In doing so, the beam paths between thecentral optical element and an optical system coordinated with it aremade to coincide. The plane in space which is defined by these parallelbeam paths may be horizontal, but it may also deviate from thehorizontal plane if the measuring points are on a different level, or ifthe outer optical elements are on a different level from the respectivemeasuring point, or both. This optical system may be active or passive,which means in this context that it can either be designed so as to sendout a beam with parallel rays towards the central element and further toa I the two measuring points, or it can be arranged for the observationor recording of light sent out from the two BRIEF SUMMARY OF THEINVENTION The foregoing and other objects which will be apparent fromthe following description are achieved according to the presentinvention by providing, in a device of the type described, a centraloptical element which is rotatable about an axis parallel to thesemitransparent and totally reflective surfaces thereof.

DETAILED DESCRIPTION There follows a detailed description of a preferredIn FIG. 1, the numeral designates the central optical system, which inthis case comprises a laser, by means of which a concentrated light beamis emitted towards the central optical element 11. This brings about adivision of the beam path from the optical system 10 into two beams 31which are parallel to one another and oriented in opposite directions toone another. For this purpose the central optical element comprises asemi-transparent surface 12 and a totally reflecting surface 13. Thesetwo surfaces are at a right angle to one another. By means of thesemi-transparent surface 12 a first beam path 30 is achieved towards oneof this arrangement, the beam paths directed towards the measuringpoints 16 and 17 are parallel to one another.

The device is constructed so that the distance between the two said beampaths towards the measuring points 16 and 17 can'be adjusted from aminimum distance of the order of magnitude of 15 cm to a maximumdistance of the order of magnitude of some hundred centimeters. Theinvention is not limited, however, to such a dimensioning of theapparatus for such distances between the two beam paths to be achieved.In principle, the device may be used for any distances between thesebeam paths and thus also for the measurement of the distance projectedonto a basel plane between the measuring points 16 and 17, this basalplane being at a right angle to the beam paths.

In the present embodiment, the two outer optical elements 14 and 15 aremechanically joined to the central optical element 11 in that each ofthe outer optical elements is attached to a member 18 and 19,respectively, so that a transport of the outer optical elements 14 and15 in relation to the central optical element 11 in the direction ofbeam paths 30 and 31, can be brought about. In this case member 18 isprovided with a scale 32, towards which points an index 33 attached tothe member 19, this scale having such a gradation that the distancebetween the beam paths 28 and 29 to the two measuring points 16 and 17can be read directly. Where points 16 and 17 are located in a line at aright 1 angle to beam paths 28 and 29, the distance measured embodimentof the invention, together with accompanying drawings. However, it is tobe understood that the detailed description and accompanying drawingsare provided solely for the purpose of illustrating a preferredembodiment and that the invention is capable of numerous modificationsand variations apparent to those skilled in the art without departingfrom the spirit and scope of the invention.

FIG. 1 is a diagrammatic plan view of an improved optical'deviceaccording to the present invention; and

' FIG. 2 is an enlarged diagrammatic view of a portion of FIG. 1.

is the distance between points 16 and 17. Where the line is not at aright angle to the beam paths, the distance measured is the basal planeat a right angle to the beam paths.

According to the present invention, the central optical element 11 isrotatable about an axis 20 which is parallel to the semi-transparentsurface 12 as well as to the totally reflecting surface 13.Appropriately, as shown in the drawing, this axis of rotation issituated in the middle of the semi-transparent surface 12. For rota- Theeffect that is obtained by the revolving of the central optical element11 is shown by FIG. 2 which, on a larger scale, shows this elementtogether with its cylindrical housing. In this case, the central opticalelement comprises two rectangular three-sided prisms 23 and 24 which areso joined together that the hypotenuse of the prism 23 rests against oneside, other than the hypotenuse, of the prism 24. In FIG. 2 these prismsare shown in broken lines in a position which corresponds to theposition shown in FIG. 1, whereas the fully drawn lines show theseprisms after a certain rotation about the axis 20.

In the position of the central optical element 11 shown in FIG. 1, thebeam path 25 towards the optical system and the beam path 26 towards theouter optical element 14 are at a right angle to one another. A rotationof the central optical element 1 1 over an angle V results in a changeof angle between the beam paths 25 and 26, which is greater than 2V,since the semitransparent surface 12 is a part of the prism 23 and adifiraction of the beam paths 25 and 26 as indicated in FIG. 2 occurs inthe two small sides of prism 23. The angular range V,,, which the beampath 26 in this manner can be made to sweep over, becomes consequentlyapproximately 130, in this embodiment. It will further be appreciated,that if the central optical element 11 is rotated from the positionshown in FIG. 1 anti-clockwise about 90, a beam path directed oppositelyto the beam path 26 is obtained, which then, by further rotation of thecentral optical element 11 in anti-clockwise direction, can be made tosweep over an angular range of equal size to the aforementioned one. Indoing so, as mentioned previously, the beam path 26,

and the beam path directed oppositely to it respectively, will lie thewhole time within the plane in space which is defined by the parallelbeam paths 28 and 29, thus making it possible to easily determine if agiven random point is located above or below that plane.

What is claimed is:

1. In a device for measuring the distance between two measuring pointsas projected onto a basal plane comprising a central optical elementincluding a semitransparent surface and a totally reflecting surfacelocated at a right angle with respect to said semi-transparent surface,a first outer optical element present in the beam path between saidsemi-transparent surface and a first measuring point and deflecting saidbeam path at a right angle, a second outer optical element present inthe beam path between said totally reflecting surface and a secondmeasuring point and deflecting said beam path at a right angle, theimprovement wherein said central optical element is rotatable about anaxis parallel to said semi-transparent and totally reflective surfaceswhereby said device is provided with the capability of opticallydetermining the location of a given random point relative to a planecommon to said first and second outer optical elements and said firstand second measuring points, said axis being normal to said plane. I

2. A device according to claim 1 wherein said axis is located in saidsemi-transparent surface.

3. A device according to claim 1 wherein said central optical elementcomprises two three sided rectangular prisms, the hypotenuse of oneprism being adjacent a side other than the hypotenuse of the secondprism.

* i l I. I

1. In a device for measuring the distance between two measuring pointsas projected onto a basal plane comprising a central optical elementincluding a semi-transparent surface and a totally reflecting surfacelocated at a right angle with respect to said semi-transparent surface,a first outer optical element present in the beam path between saidsemi-transparent surface and a first measuring point and deflecting saidbeam path at a right angle, a second outer optical element present inthe beam path between said totally reflecting surface and a secondmeasuring point and deflecting said beam path at a right angle, theimprovement wherein said central optical element is rotatable about anaxis parallel to said semi-transparent and totally reflective surfaceswhereby said device is provided with the capability of opticallydetermining the location of a given random point relative to a planecommon to said first and second outer optical elements and said firstand second measuring points, said axis being normal to said plane.
 2. Adevice according to claim 1 wherein said axis is located in saidsemi-transparent surface.
 3. A device according to claim 1 wherein saidcentral optical element comprises two three sided rectangular prisms,the hypotenuse of one prism being adjacent a side other than thehypotenuse of the second prism.